Alois Riehl, the Austrian neo-Kantian philosopher, was born in Bolzano. Riehl was consecutively Privatdozent (1870), extraordinary professor (1877), and professor (1878) at the University of Graz. He moved to the University of Freiburg in 1882, to Kiel in 1895, to Halle in 1898, and to Berlin in 1905.
Riehl's first philosophy was a realistic metaphysics based on Johann Friedrich Herbart and indirectly on Gottfried Wilhelm Leibniz, and it is of interest, just as in the case of Immanuel Kant, to study the relation between Riehl's precritical and critical writings.
Between 1870 and 1872 Riehl made his first realistic, monistic, evolutionist decisions within that dogmatic framework. His Realistische Grundzüge (Graz, 1870) centered on the problem of sensation, which he originally conceived as a polycentric reciprocal matrix of consciousness and movement.
In Über Begriff und Form der Philosophie (Berlin, 1872) he advocated a critical, rational requirement and the scientific character of philosophy, to which he assigned the historical task of leading to ideal ends. In Moral und Dogma (Vienna, 1872) he defended the independence of positive morality from beliefs.
A profound study of Kant freed Riehl from his metaphysical dogmatism. The first volume of his Der philosophische Kritizismus (1876) marked an important date in the history of the new Kantianism. This work highlighted the hold on Kant of the spirit of the new positive science (not so much through the influence of René Descartes as through that of John Locke and David Hume).
Combating psychological and idealistic "misconceptions" of Kant's views, Riehl proposed that the evolution of Kant's thought be studied, and successive editions of Der philosophische Kritizismus benefited from previously unpublished writings of Kant discovered by Kant philologists.
Kant, according to Riehl, clarified the method of philosophy; in abandoning metaphysics but not identifying itself with science, philosophy shows itself to be theory of knowledge and the methodology of the natural sciences.
It is false, however, to eliminate the thing-in-itself and the presupposition of realism common to the sciences, as Hermann Cohen did. Kant distinguished form from content and sought to determine the formal a priori of nature in general and not the particular laws of nature evident in the real experience of the sciences.
In the second and third volumes of Der philosophische Kritizismus (1879 and 1887) Riehl reassessed and amplified his own views. It was not easy: To do so he had to fight with Kant himself (whom Eugen Dühring had blamed for having "two centers of gravity"), even reduced to the first Critique alone.
In Riehl's view, neither dogmatic realism nor idealism, whether phenomenalist, or absolute, or positivistic, was adequate. Riehl sought to bring Kant up to date concerning the "sensible and logical foundation of knowledge" by surveying the great scientific innovations since Kant's day, such as Robert Mayer's principle of the conservation of energy and the Darwinian theory of evolution.
Only then could Riehl critically resume his own realistic monism centered on perception. But perception, the first cognition, is not, in Riehl's judgment, the first reality. The two aspects of perception—the mechanical, which can be made objective and is quantitatively determinable by positive science, and the qualitative, which is subjectively immediate and the sole revealer of the real universal reciprocity—are both phenomenon (Erscheinung), although not merely appearance (Schein); neither of the two aspects makes up "nature in itself."
The monistic propensity, leading to the threshold of metaphysics, comes upon reefs the critique must steer clear of. For example, he desires that his identification of the physical and the psychical should not be confused with materialism, or monadism, or universal psychophysical correspondence, or Spinozistic panpsychism. Again, although Riehl saw mental life as a product of natural evolution, he denied the evolutionary genesis of logical and mathematical concepts.
In 1883, in his inaugural lecture at Freiburg, "Über wissenschaftliche und nichtwissenschaftliche Philosophie," Riehl turned to other fields of philosophy with a progressive valuation (compare a lecture at Princeton, 1913: "Der Beruf der Philosophie in der Gegenwart").
Even in Der philosophische Kritizismus, confined to the naturalistic horizon, he had apologized for glancing at "the field of practical philosophy" but had at the end intimated that beyond the realm of science lay the realms of moral action and artistic production (to which he later added religion).
It may be asked whether there could be a philosophy of these things if "theoretical" is identical with "scientific" (wissenschaftliche). In his later years Riehl struggled with this problem, surrounded too by the other neo-Kantian movements.
"Feeling," which he had acknowledged as another side of experience, might be available for that theoretical purpose, but to be so available its evaluations must be freed from practical empiricism. Heinrich Rickert, who had frequent contact with Riehl, later sought to show Riehl's increasing interest in the world of values, until Riehl finally acknowledged that the role of philosophy is "to raise to conceptual clarity our knowledge of values and their system."